A motion transmission system in a bicycle comprises a chain extending between toothed wheels associated with the axle of the pedal cranks and with the hub of the rear wheel. When there is more than one toothed wheel at at least one of the axle of the pedal cranks and the hub of the rear wheel, and the motion transmission system is therefore provided with a gearshift, a front derailleur and/or a rear derailleur are provided for. In the case of an electronically servo-assisted gearshift, each derailleur comprises a chain guide element, also known as cage, movable to move the chain among the toothed wheels in order to change the gear ratio, and an electromechanical actuator to move the chain guide element. The actuator in turn typically comprises a motor, typically an electric motor, coupled with the chain guide element through a linkage such as an articulated parallelogram, a rack system or a worm screw system, as well as a sensor of the position, speed and/or acceleration of the rotor or of any moving part downstream of the rotor, down to the chain guide element itself. It is worthwhile noting that slightly different terminology from that used in this context is also in use.
Control electronics changes the gear ratio automatically, for example based on one or more detected variables, such as the travel speed, the cadence of rotation of the pedal cranks, the torque applied to the pedal cranks, the slope of the travel terrain, the heart rate of the cyclist and similar, and/or the gear ratio is changed based on commands manually input by the cyclist through suitable control members, for example levers and/or buttons.
A device for controlling the front derailleur and a device for controlling the rear derailleur—or just one of the two in the case of simpler gearshifts—are mounted so as to be easy for the cyclist to manoeuvre, normally on the handlebars, close to the handgrips thereof where the brake lever is also located for driving the front and rear wheel brake, respectively. Control devices that allow to drive both a derailleur in the two directions and a brake are commonly called integrated controls.
By convention, the device for controlling the front derailleur and the brake lever of the front wheel are located close to the left handgrip of the handlebar, and vice-versa the device for controlling the rear derailleur and the brake lever of the rear wheel are located close to the right handgrip.
The aforementioned components are located on-board the bicycle and must communicate with one another. Moreover, the aforementioned components must be powered.
U.S. application Ser. No. 14/290,646, which is incorporated herein by reference as if fully set forth and which claims priority to Italian Application No. MI2013A000895, discloses a bicycle electronic system, typically comprising a battery unit, a manual command management unit, a derailleur management unit, and a power supply and communication bus, each of said units being connected to said bus. The bicycle electronic system can include other management unit or units of a different type selected from the group consisting of a computer cycle, a sensor unit, a logging unit, a peripheral unit, all connected to the supply and communication bus.
In such a known bicycle electronic system, each unit other than the battery unit comprises a processor and is suitable for transmitting and receiving messages over the power supply and communication bus according to a communication protocol. Such communication protocol provides, for example, that there is a single unit transmitting at one time and that all of the units are constantly able to receive.
Such a distributed architecture makes it possible to avoid a central processing unit, as well as to easily expand the system. Moreover, the power supply is advantageously shared by all of the units.
However, the Applicant has now recognised that, when the bicycle stays immobile for a long period of time, typically in the winter, the aforementioned electronic system stays in a so-called “dormant” or “standby” state. In such a state, the various units connected to the power supply and communication bus, for example the respective processor, continue to absorb current from the battery unit, which thus tends to run down. This problem is increased in severity as the number of units of the bicycle electronic system increases. The same drawback is also encountered in the case of the absence of a processor in each unit, due to the absorption of current by other components of the various units.
The problem at the basis of the invention is therefore that of avoiding the aforementioned drawback, in particular by providing a bicycle electronic system having a device for switching-off/(re)switching-on, and a method for switching-off/(re)switching-on, which are easy for the user to use and that at the same time ensure high reliability of operation.